DESCRIPTION (provided by investigator): About 10-15% of couples suffer from infertility and its prevalence is increasing in the United States. Use of infertility services constitutes a major economic burden, and success rates of treatment are relatively low. We propose to conduct an internet-based feasibility study of risk factors for delayed time-to-pregnancy (TTP), a sensitive indicator of a couple's fertility. With targeted internet advertisements on FACEBOOK (popular social- networking website) and other social- and health-related websites, we will recruit a cohort of 2,500 female residents of Massachusetts aged 21-44 years who are planning a pregnancy. To increase minority enrollment, we will oversample African American (20%) and Hispanic (15%) women. After a short run-in period to verify a participant's identity and willingness to participate in a year-long study, participants will be followed using web-based questionnaires every 8 weeks for 12 months or until clinically-recognized pregnancy occurs, whichever comes first. The male partners of female participants will be asked to complete a web- based baseline questionnaire on lifestyle and medical history. Half of enrolled women will be randomized at baseline to receive free access to web-based menstrual charting software (FertilityFriend.com), available to them via both computer and smartphone. The primary aim of the study will be to assess the feasibility, validity, and efficiency of using the internet for recruitment, follow-up, and data collection. Secondarily, it will evaluate several potential risk factors for delayed TTP, including caffeine, anthropometric factors, physical activity, and antidepressant use. Thirdly, it will assess whether use of the web-based menstrual charting software increases cohort retention and shortens TTP. In a subset of women who conceive and deliver births during the first 12 months of the study, we will link questionnaire data with birth registry data from the Massachusetts Department of Public Health Registry of Vital Records. Registry data will be used to validate self-reported TTP and other questionnaire data (e.g., prepregnancy body mass index). We have given priority to common risk factors for which existing studies of their relation to TTP are inconclusive. The proposed prospective design is novel because most studies of fecundability have evaluated the TTP retrospectively among women who become pregnant, a method prone to selection and recall biases. Moreover, no previous TTP study has evaluated the impact of incorporating web-based menstrual charting software into its protocol. The internet will allow us to identify women planning a pregnancy, a challenging population to target using traditional epidemiologic methods. Recently, our research team demonstrated that internet-based methods are an efficient and cost-effective means of recruitment and follow-up in a prospective cohort study of TTP in Denmark. However, the feasibility of these methods remains to be tested in the United States. Such a design could have far-ranging implications for the practice of epidemiology.